Accommodation-convergence association; experiments with phenylephrine, pilocarpine, and physostigmine.

Introduction In a recently published paper 1 data were described which showed that the amount of convergence associated with a given change in the dioptric stimulus to accommodation is greatly increased when the eyes are under cycloplegia induced by homatropine over that when they are in the normal state. This phenomenon was first described by Maddox and more recently by Morgan. 2 As measured quantitatively, homatropine causes a marked increase in the accommodative convergence-accommodation (stimulus) ratio [(A — C)/A] over that ratio measured normally. The increase seems to vary as a function of the degree of cycloplegia. The data were obtained by the fixation-disparity technique. With this technique of measuring ocularmotor imbalance, extrafoveal binocular vision and fusion are maintained throughout the test and both eyes are subjected simultaneously to the same dioptric stimulus to accommodation. Most interestingly, the data showed that in the presence of homatropine cycloplegia the change in